<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>画三个盒子</title>
    <style>
        .blue {
            width: 150px;
            height: 150px;
            /* 背景颜色 background */
            background-color: #37d9f6;
        }

        .green {
            width: 150px;
            height: 150px;
            background-color: greenyellow;
        }
    </style>
</head>

<body>
    <div class="blue"></div>
    <div class="green"></div>
    <div class="blue"></div>
</body>

</html>